A Kununurra resident took this photo of the saltwater crocodile in the lake.

Supplied

A large and dangerous saltwater crocodile has turned up in the freshwater Lake Kununurra, close to a township, after bypassing dam walls.

Authorities said it was the first time in several years a "saltie" had made its way into the popular lake, home to hundreds of relatively harmless freshwater crocodiles.

A Kununurra resident photographed the animal near Calton Gorge this morning.

Department of Parks and Wildlife officer Matt Byers said the animal's size was a concern and authorities were working to remove it from the waterway.

"We're thinking it's between the two-and-a-half- and three-metre mark," he said.

"An animal that size can pose a significant risk to humans.

"We'll be heading out this afternoon and basically every morning and evening until we can locate the animal."

While crocodiles sighted in remote rivers and waterholes are generally left alone, Lake Kununurra falls within a designated "risk mitigation area", in which all saltwater crocodiles have to be either removed or destroyed.

Aboriginal rangers to help catch crocodile

Mr Byers said local Aboriginal rangers would help to find and catch the animal as quickly as possible.

"We've got a baited trap out there at present, so we're asking people to be mindful of that and not approach the trap," he said.

"Other than that, we'll be going out in the evenings and conducting spotlight surveys with a view to spotting it and harpooning it, and as a last resort we can destroy it.

"Harpooning is basically physically harpooning the animal and getting it into the vessel that way, and then we can manage the animal with various methods - roping it and taping it - and then we can remove it from the waterway."

It is an unusual time for crocodiles to be on the move in the Kimberley.

Normally during the cooler dry-season months, the animals stay in one area and sightings are less frequent.

Anyone who sees the crocodile is asked to contact the Department of Parks and Wildlife immediately, and if possible, photograph it from a safe distance.